docs: def update_metadata(source, target) -> None:
      """Update the namespace and annotation metadata in the target graph.
  
      :param pybel.BELGraph source:
      :param pybel.BELGraph target:
      """
      target.namespace_url.update(source.namespace_url)
      target.namespace_pattern.update(source.namespace_pattern)
  
      target.annotation_url.update(source.annotation_url)
      target.annotation_pattern.update(source.annotation_pattern)
      for keyword, values in source.annotation_list.items():
          if keyword not in target.annotation_list:
              target.annotation_list[keyword] = values
          else:
              target.annotation_list[keyword].update(values)